Fluorescent material



Oct. 4, 1938. w. A. ROBERTS FLUORESCENT MATERIAL Filed Oct. 6, 1956 l3 l5 E; /a a Irwvehtor: Willard AJQ befts, by WW5 H l s ACto rn ey.

Patented Oct. 4, 1938 PATENT OFFICE,

FLUORESCENT MATERIAL Willard A. Roberts, Cleveland Heights, .Ohio, assignor to General Electric Company, a corporation of New York Application October 8,

13 Claims.

My invention relates to the composition and manufacture of luminous materials, more particularly fluorescent materials,- which become luminous under the action of electric discharges.

This case is a continuation-in-part of my application Serial No. 75,782, filed April 22, 1936.

One of the objects of my invention is to provide such materials which are highly eillcient in converting impinging radiant energy into fluorescent light. Another object is to obtain a crystal structure in the material which improves its adaptability for application to the glass surface of enclosures of electric discharge devices.

It has been known that calcium tungstate has material has heretofore been prepared by heating together calcium oxide and tungstic oxide in the proper chemical proportions to produce calcium tungstate. To this was also added a crease the efficiency of the material.

According to my invention, an improved blue fluorescing material may be made by heating together calcium oxide or a calcium compound, such as calcium carbonate, which will decompose when heated in the air to give calcium oxide at a temperature lower than that required to form the fluorescent material; tungsten oxide, tungstic acid or some material which decomposes when heated in the air to give tungstic oxide at a temperature lower than that required to form the fluorescent material; and an exciter such as a soluble lead compound, preferably lead acetate.

The proportions of the calcium compound and tungstic oxide are preferably such that from one to ten per cent more calcium oxide is used than is required by the chemical formula Ca'WOr. This produces a mixture which gives greater fluorescence when subjected to ultra-violet radiations of 2537 angstroms than does the ordinary compound. The lead is added as a soluble salt in an amount such that lead is present in the quantity of 0.5% to 1.5% of the total weight.

Mixtures of twenty-one parts of CaO, seventynine parts of W03, and about 1.0% of lead, by weight, gave approximately fifteen to twenty per cent more light than CaWOr.

The drawing is a side elevation, partly in section, of a form of lamp in which the abovedescribed materials may be used, the particular lamp illustrated being describedand claimed in the U. S. patent application of George E. Inman, Serial No. 75,772, filed April 22, 1936.

Referring to the drawing, the lamp comprises a tubular glass container I having a pair of the property of fluorescing with a blue light. This small amount of an "exciter such as lead to in-- 1936, Serial No. 104,239

thermionic electrodes II at the ends thereof. Each of said electrodes H consists of a filament of refractory wire, preferably tungsten, coiled on a mandrel, also preferably of tungsten, a portion of this coil on mandrel (shown as a single line in 6 the drawing) being coiled again into a spiral as shown in the drawing and this spiral portion being covered with an electron emitting material such as barium oxide. The ends of the container ID are closed by discs l2 of a metal or alloy, such as a chrome-iron alloy, sealed directly to the ends of the container. The discs l2 are of the type described and claimed in U. S. patent application of Harold D. Blake, Serial No. 3,334, filed January 24, 1935, and comprise recesses 13 which increase in diameter and are adapted to be engaged by holders having clip portions which snap into the said recesses. One of the discs l2 has an opening I 4 at the center of the recess it! through which the container I0 is exhausted and filled with a suitable gas or gases, the said opening I4 being subsequently sealed by the residue 15 of the glass exhaust tube. The electrode II is attached to the transversely extending end portion l6 of a support wire ii, the other end I8 01' which encircles the boss formed at the inside of the disc l2 by the recess l3. The container II has a starting gas therein such as argon and a quantity I! of vaporizable metal, preferably mercury. During the operation of the device the electrically excited mercury vapor emits visible and ultra-violet light. For ease of starting, a strip 2| of conductive material such as a metal powder or graphite is applied to the container III and is in contact with one of the discs l2 and extends to a position adjacent the electrode II at the opposite end of the container.

The inner surface of the container l0 has applied thereto a coating 2| of the luminescent material described above. The coating 2| may be applied to the surface of the container by means of a binder, or it may be embedded in the glass itself by heating the glass to its softening point or, if the powdered material is fine enough, it will adhere when it is merely dusted into the container. Among the various binders which may be used are glycerin; glycerin and twenty per cent of boric acid; phosphoric acid alone or diluted with acetone or alcohol; potassium silicate; an ester of glycerin with boric acid; castor oil or mineral oil; 50 or an inorganic resin such as that sold under the name of "Stacol" by the Glyco Products Co., Inc., of Brooklyn, N. Y. During the operation of the lamp the ultra-violet rays striking the luminescent material are transformed thereby into visible 5s light rays which complement and supplement the spectrum of the visible light emitted by the electrically excited gaseous atmosphere. Efliciencies of 22 lumens per watt have been obtained with a lamp of the type described using materials of the type comprising my invention. I

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A fluorescent material for electric discharge lamps comprising calcium oxide and tungstic oxide, the calcium oxide being in excess of the amount required by the chemical formula CaWOe 2. A fluorescent material for electric discharge lamps comprising calcium oxide, tungstic oxide and a small quantity of an exciter, the calcium oxide being in excess of the amount required by the chemical formula CaWO4.

3. A fluorescent material for electric discharge lamps comprising calcium oxide, tungstic oxide and a small quantity of lead, the calcium oxide being in excess of the amount required by the chemical formula CaWO4.

4. A fluorescent material for electric discharge lamps comprising calcium oxide and tungstic oxide, the calcium oxide being present in an amount of from one to ten per cent more by weight than is required by the chemical formula CaW04.

5. A fluorescent material for electric discharge lamps comprising calcium oxide, tungstic oxide and a small quantity of an exciter, the calcium oxide being present in an amount of from one to ten per cent more by weight than is required by the chemical formula CaW04.

6. A fluorescent material for electric discharge lamps comprising calcium oxide, tungstic oxide and a small quantity of lead, the calcium oxide being present in an amount of from one to ten per cent more by weight than is required by the chemical formula CaWO4.

7. A fluorescent material for electric discharge lamps comprising by weight approximately twenty parts of CaO and eighty parts of W01.

8. A fluorescent material for electric discharge lamps comprising by weight approximately twenty parts of CaO, eighty parts of W0; and a small quantity of an exciter.

9. A fluorescent material for electric discharge lamps comprising by weight approximately twenty parts of CaO, eighty parts of W0: and a small quantity of lead.

10. A fluorescent material for electric discharge lamps comprising by weight approximately twenty parts of CaO, eighty parts of W0: and up to two parts of lead.

11. A fluorescent material for electric discharge lamps comprising calcium oxide and tungstic oxide and up to about one and a half per cent by weight of an exciter to increase the luminosity of the material when excited, the calcium oxide being present in an amount of from one to ten per cent more by weight than is required by the chemical formula CaWO4.

12. A fluorescent material for electric discharge lamps comprising calcium oxide and tungstic oxide and up to about one and a half per cent by weight of lead to increase the luminosity of the material when excited, the calcium oxide being present in an amount of from one to ten per cent more by weight than is required by the chemical formula CaWO4.

13. A fluorescent material for electric discharge lamps comprising by weight approximately twenty parts of CaO, eighty parts of W0: and about one per cent by weight of lead.

WILLARD A. ROBERTS. 

